It is known that one can increase the capacity of a PVC reactor by maintaining the temperature of the polymerization system constant and using more active free-radical initiator. However, since the molecular weight of PVC is determined to a great extent by temperature the molecular weight of the product will not be increased by use of a more active free-radical initiator used under the same temperature conditions. Furthermore, in the case of styrene polymerizations, use of a more active free radical initiator results in a decrease in molecular weight under the same polymerization conditions. If the temperature of the system is increased at constant initiator concentration the rate of polymerization will increase but the molecular weight will decrease. A significant change in polystyrene molecular weight causes changes in the physical properties of the resulting polystyrene. The compounds of the present invention provide an increased rate of polymerization without loss of polymer properties.